Post-tensioning involves threading high-strength steel cables through ducts in concrete and then stressing them with hydraulic jacks to compress the structure. The forces involved are enormous, and a cable failure or jack malfunction during stressing can release lethal stored energy. This talk covers the hazards of post-tensioning operations and the controls required to protect everyone on site.
Key Hazards
Cable snap releasing stored energy with lethal force during stressing
Hydraulic jack failure causing uncontrolled release of the tendon
Crushing injuries from heavy strand coils and anchorage components
Grout injection under pressure causing burns or eye injuries
Control Measures
Establish an exclusion zone behind the stressing jack and along the tendon line during all operations.
Ensure only trained and competent post-tensioning operatives carry out stressing and grouting work.
Inspect all hydraulic jacks, pumps, hoses, and gauges before each stressing operation.
Verify tendon elongation measurements match the design specification before locking off strands.
Use calibrated pressure gauges and check calibration certificates are within their valid period.
Wear full face shields and heavy-duty gloves during all grouting operations under pressure.
Brief all site personnel on the exclusion zone locations before stressing operations commence.
Secure strand coils during storage and handling to prevent uncontrolled uncoiling.
Record all stressing forces, elongations, and grouting pressures in the post-tensioning log.
Emergency / Rescue
If a tendon fails during stressing, evacuate the exclusion zone immediately. Do not approach the stressing end until the hydraulic system is fully depressurised and the area declared safe by the post-tensioning supervisor.
Remember
Exclusion zones must be established behind the jack and along the full tendon line
Only trained and competent specialists may carry out post-tensioning stressing and grouting
All hydraulic equipment must be inspected and calibrated before each stressing operation
Tendon elongation must match the design specification before strands are locked off
Full face shields and heavy-duty gloves are mandatory during grout injection under pressure
Applicable Legislation: CDM Regulations 2015 · PUWER 1998 · BS EN 13670 (Execution of Concrete Structures) · Health and Safety at Work etc. Act 1974